Expanding broadband emission in the near-IR via energy transfer between Er3+–Tm3+ co-doped tellurite-glasses

Processes of energy transfer in Er3+–Tm3+ co-doped tellurite glasses has permitted to obtain an expanding broadband emission in the near-infrared region covering the bands S, C+L and U of the optical telecommunications and extending up to the 1700–1900 nm range under excitation by a 976 nm laser diode. This widening of the emission band is achieved through an integrated emission, where the Er3+ ions act as donor and the Tm3+ ions as acceptor following the route (Er3+)4I11/2→(Tm3+)3H5, (Er3+)4I13/2→(Tm3+)3H4 and (Er3+)4I13/2→(Tm3+)3F4. The relative intensity emission and lifetime of the 4I13/2→4I15/2 transition of the Er3+ ions decrease with increasing the Tm3+ concentration. Besides, high Tm3+ concentrations produce an emission quenching for the 3H4→3F4 and 3F4→3H6 radiative transitions, due to cross-relaxation between Tm3+ ions. These effects are studied by means of probability and quantum yield of the energy transfer. The most intense and widest emission band is measured in the glass co-doped with 0.075 and 1 mol% of Tm2O3 and Er2O3, respectively.